Troubleshooting Series-How to Solve Muffler Icing in Air-Operated Double Diaphragm Pumps

https://www.linkedin.com/company/dyi-sheng-industry-co-ltdWhy Does Water Vapor or Icing Occur at the Exhaust of AODD Pumps?

Air-Operated Double Diaphragm (AODD) pumps are widely used in industries such as chemical, coatings, food, and wastewater treatment due to their durability and ability to handle high-viscosity liquids and solids. However, many operators encounter issues such as “water vapor at the exhaust” or “frost/icing on the muffler,” which can reduce pump efficiency and even cause shutdowns.

The main cause lies in the expansion of compressed air as it is expelled from the pump to the external environment. This rapid expansion leads to a sudden drop in temperature. The small-pore structure of the muffler further amplifies this cooling effect through the Joule-Thomson phenomenon. If the compressed air contains a high moisture content, ice can form along the exhaust piping and frost can appear on the muffler surface, especially in humid or low-temperature environments.

Common Signs of Muffler Icing

Unstable Pump Operation: Ice blocking the exhaust holes causes restricted airflow, leading to unstable pump operation or even mechanical jamming, which reduces work efficiency.

Visible Frost or Ice on the Muffler Surface: Moisture-laden exhaust air condenses and freezes, forming noticeable frost or ice on the muffler.

If not addressed promptly, icing can not only affect pump efficiency but also accelerate component wear, increase the risk of downtime, and raise unnecessary maintenance costs.

How to Prevent and Resolve Muffler Icing

Improving AODD pump icing requires controlling air pressure, quality, and exhaust conditions. Common solutions include:

Improve Compressed Air Quality

Install an Air Preparation Unit (FRL): Removes excess moisture and contaminants, adds proper lubrication, and, if necessary, antifreeze agents.

Use an Air Dryer: Eliminates most moisture and impurities at the source.

Install Air Line Heaters: Raises air temperature to ensure exhaust temperature remains above freezing.

Adjust Pump Operating Conditions

Reduce Inlet Pressure: Lower the pressure difference to reduce the temperature drop. Set the pump to operate at the minimum pressure required for the desired flow rate.

Increase Pump Size: For higher flow requirements, selecting a larger pump can reduce inlet pressure and operating speed, alleviating icing while preventing high-pressure/high-speed wear.

Optimize Exhaust Methods

Extend the Exhaust Line: Position the exhaust outlet farther from the pump so the cooling effect occurs away from the pump body, minimizing its impact.

Increase Muffler Volume: A larger muffler or split-flow design reduces the pressure drop during exhaust, minimizing frost formation.

Perform Regular Maintenance

Pump Maintenance: Prevent dust or oil buildup that can act as icing nucleation points on the muffler, check valves, and internal piping.

Air System Maintenance: Ensure compressors and air dryers operate properly.

Conclusion

Ice formation in the exhaust piping and muffler is a common issue for AODD pumps in humid or low-temperature conditions. It originates from high moisture content in the compressed air and large pressure differences, which cause the gas temperature to drop and form ice that obstructs the exhaust path. By improving air quality, optimizing exhaust methods, adjusting operating conditions, and performing regular maintenance, icing risks can be significantly reduced, extending pump life and ensuring stable operation.

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